Chemistry is described that should serve as the basis for the chemical recognition and analysis of peptide hormones in their biological milieu. The basis of the assay is the fact that many peptide hormones possess carboxylterminal amide functionality; the chemistry described is specific for this functional group. Once the chemistry has been developed, it will be "field-tested" with extracts of biological tissues known to contain peptide hormones and then applied to the discovery of new peptide hormones in other tissues. The method in principle is more sensitive than existing methods by several orders of magnitude, and may lead to the identification of hitherto unrecognized peptide modulators of diverse biological responses.